Explosionproof switch device



June 23, 1942. A. ToRNBLoM 2,287,650

EXPLOSION-PROOF SWITCH lDEVICE Filed May 31, 1940 cfg/yl. 2

Patented June 23, 1942 FFICE EXPLOSIONPROOF SWITCH DEVICE Nils A. Tornblcm, Chicago, Ill., assigner to Appleton Electric Company, a corporation of Illinois Application May 31, 1940, Serial No. 338,068

3 i Claims.

The object of the present invention is to prevent the possibility of causing arcing at the switch to result in the ignition of combustible gases in the atmosphere loutside of the switch box.

A further object of the present invention ,is to produce a switch box so constructed that the switch may be sealed'in an explosion proof cham-` b-er with leading-in wires exposed within the box, whereby the box need konly be opened at the point of use to permit connections to be made between the wiring system and the 4said leadingin wires, and the box be then tightly closed, at the time of installation, without breaking the seal of the protective chamber within which the switch is contained.

A further object of the present invention is so to construct the device just described that when necessary to do so, the switch may be exposed and may then, with proper care, again be effectively sealed in its container.

The various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawing, wherein:

Figure 1 is a top plan view of somewhat more than one-half of a box embodying the present invention; Fig. 2 is a section taken approximately on line 2-2 of Fig. 1; Fig. 3 is a section on line 3 3 of Fig. 2; and Fig. 4 is a section at right angles to the plane of Fig. 2, illustratingthe support at one end of the switch.

Referring to the drawing, I is a box open at the top and provided with internally-threaded sleeve-like hubs 2 to receive the ends of pipes or conduitsadapted. to house cables or conductors which are to be controlled by a switch in the box. The box is provided around the top with a wide, flat flange 3, the face of which is machined so as to make an explosion-proof joint with a cover 4; the under face of the cover being machined so as to fit directly against the face of the flange. The cover may be secured in place in any suitable manner as, for example, by means of screws 5. ,u

A switch device 6 is located within a small cup-shaped container 'l which is considerably deeper than the bodyportion of the switch and is provided at the top with a flange 8 similar to the flange 3 on the box; the flange 8 fitting 'i the. actuator.

tightly against the under side of the cover and being held in place by screws 9.

The switch device 6 may be supported in any desired manner. In the arrangement shown, there is secured on top of the body member thereof ya metal plate` lil which projects beyond opposite sides of the body member and overlies ears l l projecting inwardly from the adjacent walls of the container T. Screws I2 extending through the plate I0 and into the ears 4hold the switch device in place. The switch is illustrated as being one that has an oscillatory operating lever l@ projecting upwardly through the top thereof. The cover 4 is provided on the under side with a pocket or recess i5 in which the upper end of this lever plays.

The switch lever Vmay be moved back and forth by any suitable means extending through the cover in a manner to produce an explosion-proof joint with the latter. In the arrangement shown, there is a short shaft I8 extending through and in screw-threaded engagement with the cover; the cover being thick enough to insure that any gas or flame that might seek to pass to the exterior of the box along the shaft would need to traverse such a long path that the ame would be extinguished and the gas cooled before either could reach the exterior of the box. Fixed to the inner or lower end of the shaft is a radial arm Il, the outer end of which is in the form of a fork that straddles Vthe switch lever. I prefer to place within the jaw of the fork a ring I8 that is peripherally grooved so as to be Slidable lengthwise of the fork while held against relative movements in opposite directions; this ring surrounding the switch lever and providing the actual means of contact between the same and The shaft I6 may be turned by means of a iinger piece I9 fixed to the upper or outer end thereof. Of course, the shaft I 6 moves slightly in the lengthwise direction when it is turned; but, since it may be turned through only a small angle in passing from one position to another, the effect of the lengthwise movement of the shaft on the driving connection with the switch lever is negligible.

In order that the switch may remain sealed within its special container while connections are being made to the wires of the system in which the switch is being installed, I provide the switch with wiresthat are carried to the exterior of the container 1, sealing the openings through which the wires pass. In the arrangement shown, there are two wires 28 which extend from the switch through a deep well or pocket 2| in the bottom and adjacent to one side of the container, and thence through holes 22 in the bottom wall of the container. This well or pocket, which is preferably open at the top, is filled with a sealing compound 23. Because of the depth of the well or pocket and the intimate contact of the sealing compound with the conductors, or their insulating sheathings, no flame or gases can escape from within the container 'I along the conductors.

Because the container I is not as deep as the box itself, the wires 20 may be led in any direction to a side wall of the box. The important factor, however, is that with the box open, the wires 20 can be connected to wires entering the box, without in any way disturbing the switch or sealing of the chamber within which it is housed. The act of closing the cover serves to position the switch within the box and at the same time produce an explosion-proof joint between the cover and the box.

While I have illustrated and described with particularity only a single preferred form of my invention, I do not desire to be limited to the exact structural details thus illustrated and described; but intend to cover all forms and arrangements which come within the definitions of my invention constituting the appended claims.

I claim:

1. In combination, a connection box having a one-piece detachable cover, a solid-walled open-top container for a switch underlying and having the top thereof closed by the cover, means concealed by the cover when the latter is on the box for securing the container to the cover, both the box and the container having wide endless bearing faces engaging with the under side of the cover, the width of said bearing faces being so great that any flame which may enter between the same from within the container will be extinguished before reaching the space in the box surrounding the container, a switch in the container, an actuator for the switch extending through the cover, and conductors extending from the switch through and sealed in a wall of the container.

2. In combination, a connection box having a one-piece detachable cover, a solid-walled open-top container for a switch underlying and having the top thereof closed by the cover, means extending up through a part on the container and into the cover for securing the container to the cover, both the box and the container having wide endless bearing faces engaging with the under side of the cover, the width of said bearing faces being so great that any flame which may enter between the same from within the container will be extinguished before reaching the space in the box surrounding the container, a switch in the container, an actuator for the switch extending through the cover, said container having therein a deep well open at the top and provided at the bottom with openings leading to the exterior of the container, conductors extending from the switch through said well and out in the box, and a sealing compound filling the well.

3. In combination, a connection box having a detachable cover, a solid-walled open-top container for a switch underlying and having the top thereof closed by the cover, means securing the container to the cover, the container having a wide endless bearing face engaging with the cover, the width of said bearing face being so great that any flame which may enter between the same and the overlying cover from within the container will be extinguished before reaching the space in the box surrounding the container, a switch in the container, an actuator for the switch including a shaft extending through the cover, a radial arm xed to the inner end of said shaft, a ring slidable lengthwise of the arm but interlocked therewith against relative movements in other directions, a lever extending from said switch loosely through said ring, and conductors extending from the switch through and sealed in a wall of the container.

NILS A. TORNBLOM. 

